---
id: CVE-2026-89712
title: 'NFSD: restart ssc_expire_umount walk after dropping nfsd_ssc_lock'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  NFSD: restart ssc_expire_umount walk after dropping nfsd_ssc_lock

  nfsd4_ssc_expire_umount() walks nn->nfsd_ssc_mount_list with
  list_for_each_entry_safe(ni, tmp, ...). …
severity: critical
cvss: 9.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
cwe:
  - CWE-825
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= a4bc287943f5695209ff36bdc89f17b48d68fae7 <
    2b59029b8f24a99b5d844af2da3950d39d36eeea
  - >-
    Linux >= f4e44b393389c77958f7c58bf4415032b4cda15b <
    d9e151fea5ed706c1284adacabd869b0be745db2
  - >-
    Linux >= f4e44b393389c77958f7c58bf4415032b4cda15b <
    659ee3da073164e1e6e40dfcbc26eeed85845f93
  - >-
    Linux >= f4e44b393389c77958f7c58bf4415032b4cda15b <
    60680ae7243b22de3d09be990d8e23bcfc4af837
  - >-
    Linux >= f4e44b393389c77958f7c58bf4415032b4cda15b <
    77de363d9a1c8cd35f20482782c612cda085791a
  - >-
    Linux >= f4e44b393389c77958f7c58bf4415032b4cda15b <
    4ed8d2317aef21cc2a9e5a55d6b59860b4b151a8
  - >-
    Linux >= f4e44b393389c77958f7c58bf4415032b4cda15b <
    7377fa964b8aaf47cb04e5efcc4c82d15e8c2ce9
  - >-
    Linux >= f4e44b393389c77958f7c58bf4415032b4cda15b <
    036c1b182f4da65363e79ec0ac276edc6b7296e5
  - Linux >= 5.10.220 < 5.10.270
  - Linux 5.14
published: '2026-09-11'
updated: '2026-10-19'
sourceUpdated: '2026-10-19T08:51:25.202Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-89712'
references:
  - url: 'https://git.kernel.org/stable/c/2b59029b8f24a99b5d844af2da3950d39d36eeea'
  - url: 'https://git.kernel.org/stable/c/d9e151fea5ed706c1284adacabd869b0be745db2'
  - url: 'https://git.kernel.org/stable/c/659ee3da073164e1e6e40dfcbc26eeed85845f93'
  - url: 'https://git.kernel.org/stable/c/60680ae7243b22de3d09be990d8e23bcfc4af837'
  - url: 'https://git.kernel.org/stable/c/77de363d9a1c8cd35f20482782c612cda085791a'
  - url: 'https://git.kernel.org/stable/c/4ed8d2317aef21cc2a9e5a55d6b59860b4b151a8'
  - url: 'https://git.kernel.org/stable/c/7377fa964b8aaf47cb04e5efcc4c82d15e8c2ce9'
  - url: 'https://git.kernel.org/stable/c/036c1b182f4da65363e79ec0ac276edc6b7296e5'
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89712.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-89712'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2532255'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-89712'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89712'
  - url: >-
      https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89712.mbox
tags:
  - cve.org
  - csaf
  - vex
  - red-hat
  - score-dispute
epss: 0.00714
epssPercentile: 0.53475
scores:
  cna: 9.8
  vendor: 7
ingestedAt: '2026-09-14T15:23:07.449Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

NFSD: restart ssc_expire_umount walk after dropping nfsd_ssc_lock

nfsd4_ssc_expire_umount() walks nn->nfsd_ssc_mount_list with
list_for_each_entry_safe(ni, tmp, ...).  For each expired entry it
sets nsui_busy = true, drops nfsd_ssc_lock to run mntput() on the
source vfsmount, then reacquires the lock to list_del + kfree the
entry and continue iterating via the macro's saved tmp pointer.

The nsui_busy flag protects the current ni from concurrent
nfsd4_ssc_setup_dul() finders during the lock-drop window, but it
does not pin tmp.  Another nfsd RPC thread that fails its source-
server mount and reaches nfsd4_ssc_cancel_dul() will, during that
same window, take nfsd_ssc_lock, list_del + kfree its own ssc_umount
item, and release the lock.  If that item is the saved tmp of the
expire walk, the next iteration dereferences a freed
nfsd4_ssc_umount_item.

Restart the walk from the head after the mntput() unlock window so
no saved next pointer survives the lock-drop.  The list is bounded
by the number of active inter-server source mounts (typically small)
and the expire delayed-work runs periodically rather than per-IO,
so the restart is cheap.

## Affected

- `Linux >= a4bc287943f5695209ff36bdc89f17b48d68fae7 < 2b59029b8f24a99b5d844af2da3950d39d36eeea`
- `Linux >= f4e44b393389c77958f7c58bf4415032b4cda15b < d9e151fea5ed706c1284adacabd869b0be745db2`
- `Linux >= f4e44b393389c77958f7c58bf4415032b4cda15b < 659ee3da073164e1e6e40dfcbc26eeed85845f93`
- `Linux >= f4e44b393389c77958f7c58bf4415032b4cda15b < 60680ae7243b22de3d09be990d8e23bcfc4af837`
- `Linux >= f4e44b393389c77958f7c58bf4415032b4cda15b < 77de363d9a1c8cd35f20482782c612cda085791a`
- `Linux >= f4e44b393389c77958f7c58bf4415032b4cda15b < 4ed8d2317aef21cc2a9e5a55d6b59860b4b151a8`
- `Linux >= f4e44b393389c77958f7c58bf4415032b4cda15b < 7377fa964b8aaf47cb04e5efcc4c82d15e8c2ce9`
- `Linux >= f4e44b393389c77958f7c58bf4415032b4cda15b < 036c1b182f4da65363e79ec0ac276edc6b7296e5`
- `Linux >= 5.10.220 < 5.10.270`
- `Linux 5.14`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Vendor advisories

- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · updated 2026-09-21 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89712.json)